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bytes vs bitmapData - Mac Programming

I'm loading an image into a NSBitmapImageRep object and a NSData object, but when I get the raw data using -bitmapData and -bytes they appear to be different, at least when loaded as an OpenGL texture. What is the difference between NSBitmapImageRep's -bitmapData and NSData's -bytes? And why is there a difference?...

  1. #1

    Default bytes vs bitmapData

    I'm loading an image into a NSBitmapImageRep object and a NSData object,
    but when I get the raw data using -bitmapData and -bytes they appear to
    be different, at least when loaded as an OpenGL texture. What is the
    difference between NSBitmapImageRep's -bitmapData and NSData's -bytes?
    And why is there a difference?
    Edward Hillenbrand Guest

  2. #2

    Default Re: bytes vs bitmapData

    In article <20030827204605328-0700news.sf.sbcglobal.net>,
    [email]elihREMOVEsbcREMOVEglobal.net[/email] says...
    > I'm loading an image into a NSBitmapImageRep object and a NSData object,
    > but when I get the raw data using -bitmapData and -bytes they appear to
    > be different, at least when loaded as an OpenGL texture. What is the
    > difference between NSBitmapImageRep's -bitmapData and NSData's -bytes?
    > And why is there a difference?
    >
    If you load a file into NSData then 'bytes' will give you the bytes from
    the file a bit like loading the image into a hex editor so you'll have
    all the file headers, preview images, padding, comments, compressed
    data, etc. Unless you're interested in the file rather than the image
    this is probably not what you want.

    When loaded into an NSBitmapImageRep you are given access to the image
    data as it will be displayed on the screen. You can then use the methods
    for getting information about the image to examine or alter the pixels.
    'bitmapData' will give you a pointer to the start of the pixels and
    using methods like 'bitsPerPixel', 'bytesPerRow' and 'samplesPerPixel'
    will allow you to determine how the data is stored within the array
    returned from 'bitmapData'.
    James Weatherley Guest

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